The present invention is generally related to permanent magnet linear brakes and is more particularly directed to eddy brake systems for movable cars, for example, rail supported cars, go-carts, elevator cars, conveyor cars, and roller coaster cars, among others.
As a specific example, the majority of hereinbefore constructed entertainment rides, such as roller coasters, have relied on friction brakes for deceleration and stopping of well-mounted cars. However, due to friction, such brakes are subject to wear and must be regularly monitored and serviced to maintain proper operating conditions.
Linear eddy current brakes would be a preferable replacement for such friction brakes inasmuch as since no contact is made with the rail for braking and consequently, they are free from wear due to friction.
Eddy current brakes are based on the law of induction. When a conductive member is moved through a magnetic field, eddy currents are generated in the member and a secondary magnetic field caused by the eddy currents is opposed to the magnetic field through which the member passes.
The resulting force component acts opposite to the traveling direction of the member. Unfortunately, such eddy current brakes are motion dependant and cannot hold a vehicle or device in a fixed position or effect a total stop on an inclined rail. Thus, a separate secondary friction brake has been used to supplement an eddy current brake. This separate system adds to the cost of the total braking system, and typically requires a second brake fin for use exclusively in the friction brake.
The present invention provides for a conductive fin having dual use for the induction of eddy currents therein and for providing an engagement surface for a mechanical brake shoe.
A brake system in accordance with the present invention generally includes a linear array of spaced apart permanent magnets and a non-magnetic electrically conductive fin. The magnets and fin are mounted for enabling passage past one another at a distance sufficient to cause eddy currents to be induced in the fin resulting in a braking force between the magnets and the fin.
A mechanical brake is also provided for frictionally engaging the same fin. Importantly, a surface treating on the fin enables the fin to sustain mechanical abuse friction without effecting a changeable electrical conductivity of the fin, thus, the surface treatment enables dual use of the fin. That is, the fin function both to provide eddy current braking and frictional braking.
This dual use reduces the number of parts required and allows a more efficient use of limited space for brakes by placing both eddy current brakes and mechanical brakes in tandem along a single center line as will be hereinafter discussed in greater detail.
The surface treatment on the fin enables the fin to maintain its efficiency as a non-conductor for the induction of eddy currents.
More practically, the surface treatment may be selected from a group of coatings including, for example, hard chrome, nickel, nickel-chrome, high velocity spray coating, and electroless nickel coating.
In one embodiment of the present invention, the fin is mounted in a vertical orientation for passage by the magnets. In this embodiment, the mechanical brake may comprise a pinch brake.
In another embodiment of the present invention, the fin may be mounted in a horizontal orientation for passage by the magnets.